Re: [Linux-fbdev-devel] Re: [ACPI] inappropriate use of in_atomic()

[Andrew Morton]

(where'd my cc go?)

Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Fri, 2005-03-11 at 01:46 -0800, Andrew Morton wrote:
> > Jan Kasprzak <kas@xxxxxxxxxx> wrote:
> > >
> > > This may be the cause of 
> > > 
> > >  http://bugme.osdl.org/show_bug.cgi?id=4150
> > 
> > Looks that way, yes.
> 
> Note that it would be interesting to fix that (I mean the reliability of
> is_atomic() or an alternative). I agree it's quite bad to rely on that
> in practice, but there are a few corner cases where it's useful (like
> oops handling in fbdev's etc...)
> 

That would require that we increment current->something on every
spin/read/write_lock and decrement it in unlock, even with !CONFIG_PREEMPT.

iirc, Anton added an option to do that to the ppc64 build, decoupled from
CONFIG_PREEMPT (which ppc64 doesn't support).

But it's an appreciable amount of overhead.
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